Single reflow power pin connections

ABSTRACT

A method, in some embodiments, comprises: providing a direct bonded copper (DBC) substrate including a plurality of copper traces; providing a guide plate having protrusions on a surface of the guide plate; mounting hollow bush rings onto the protrusions; mounting the bush rings onto the copper traces by aligning the protrusions of the guide plate with solder units on said copper traces; attaching the bush rings and one or more dies to the copper traces by simultaneously reflowing said solder units and other solder units positioned between the dies and the copper traces; and after said simultaneous reflow, removing the protrusions from the bush rings.

BACKGROUND

Power integrated modules (PIMs) typically contain several powersemiconductor devices. These semiconductor devices are usually dies thatare soldered to metallic contacts on a substrate, such as copper tracesformed on a direct bonded copper (DBC) substrate having a ceramicmid-layer. The PIMs also contain power pin rings that are soldered tothe copper traces. The rings and the dies are usually solderedseparately—that is, multiple reflow processes are used. An electricalpathway is thus formed between the soldered dies and pins inserted inthe rings. When the dies are coupled to other electronic devices (e.g.,printed circuit boards (PCBs)), communications between the electronicdevices and the dies are enabled.

SUMMARY

At least some embodiments are directed to a method, comprising:providing a direct bonded copper (DBC) substrate including a pluralityof copper traces; providing a guide plate having protrusions on asurface of the guide plate; mounting hollow bush rings onto theprotrusions; mounting the bush rings onto the copper traces by aligningthe protrusions of the guide plate with solder units on said coppertraces; attaching the bush rings and one or more die to the coppertraces by simultaneously reflowing said solder units and other solderunits positioned between the die and the copper traces; and after saidsimultaneous reflow, removing the protrusions from the bush rings. Theseembodiments may be supplemented using one or more of the followingconcepts in any order and in any combination: further comprising using avacuum system to retain the bush rings on the protrusions; furthercomprising disabling the vacuum system prior to removing the protrusionsfrom the bush rings; further comprising inserting power pins into thebush rings; wherein at least one of the power pins has a dimension thatexceeds an internal wall surface-to-internal wall surface dimension of acorresponding bush ring; wherein each head of one or more of the powerpins has a width that is greatest in the center of the head andcomprises an orifice; further comprising establishing electrical contactbetween said power pins and a printed circuit board (PCB); wherein atleast one of the bush rings has a shape that is selected from the groupconsisting of: a cross-section that is substantially square whenmeasured from outer wall surface to outer wall surface and one end thatis flat, said end located in a plane that is perpendicular to thelongitudinal axis of the bush ring; a cross-section that issubstantially square when measured from outer wall surface to outer wallsurface and one end at which the wall has multiple raised portions andmultiple depressed portions, said end located in a plane that isperpendicular to the longitudinal axis of the bush ring; and across-section that is substantially square when measured from outer wallsurface to outer wall surface and one end at which the wall has multipleraised portions and multiple depressed portions, said raised portionsextending away from the longitudinal axis of the bush ring, said endlocated in a plane that is perpendicular to the longitudinal axis of thebush ring; further comprising depositing a molding onto the DBC, bushrings and die, a surface of the molding being flush with the end of atleast one of said bush rings, said end located in a plane that isperpendicular to the longitudinal axis of the bush ring; and furthercomprising using a metal or plastic clip to fasten the molding to a heatsink.

At least some embodiments are directed to a system, comprising: a directbonded copper (DBC) substrate including a ceramic layer and coppertraces on a surface of the ceramic layer; hollow bush rings soldered tothe copper traces; and a guide plate having protrusions mated with thebush rings, wherein each of said bush rings has an end at which the wallof the bush ring has multiple raised portions and multiple depressedportions, said end located in a plane that is perpendicular to thelongitudinal axis of the bush ring. These embodiments may besupplemented using one or more of the following concepts, in any orderand in any combination: wherein said ends are soldered to the coppertraces; wherein said raised portions extend away from the longitudinalaxis of the bush ring; wherein said raised portions are parallel to thelongitudinal axis of the bush ring; wherein said bush rings havesubstantially square cross sections when measured from outer wallsurface to outer wall surface; further comprising a die soldered to oneof the copper traces; and further comprising a vacuum system having airpassages positioned in the guide plate and in at least one of theprotrusions.

At least some embodiments are directed to a system, comprising: apackage; a plurality of pins protruding through orifices in the package;a direct bonded copper (DBC) substrate having a ceramic layer andmultiple copper traces on the ceramic layer, said copper traces solderedto hollow bush rings within which said pins are positioned; and one ormore die soldered to one or more of the copper traces and electricallycoupled to one or more of the pins, wherein each of the bush rings hasan end at which the bush ring wall has raised portions and depressedportions, said end in a plane that is perpendicular to the longitudinalaxis of the bush ring, wherein said ends are soldered to the coppertraces. These embodiments may be supplemented using one or more of thefollowing concepts, in any order and in any combination: wherein each ofsaid pins has two heads, at least one of said two heads having atapering shape and an orifice; and wherein said raised portions of thebush ring wall extend away from the longitudinal axis of the bush ring.

BRIEF DESCRIPTION OF THE DRAWINGS

There are disclosed in the drawings and in the following descriptiontechniques for establishing power pin connections in power modules usinga single reflow process. In the drawings:

FIG. 1 shows a perspective view of a DBC substrate having copper tracesto which printed solder units and dies are mounted.

FIG. 2 shows a perspective view of a guide plate having multipleprotrusions.

FIGS. 3A-3K illustrate perspective views of various embodiments of abush ring.

FIG. 4 shows a perspective view of a guide plate having multipleprotrusions, one of which has a bush ring mounted thereupon.

FIG. 5A illustrates a perspective view of a guide plate having multiplebush rings being flipped onto a DBC substrate so that the bush ringscontact the solder units printed on the DBC substrate copper traces.

FIG. 5B shows a cross-sectional view of a guide plate vacuum system.

FIG. 6 shows a perspective view of a DBC substrate having multiple bushrings and dies simultaneously soldered thereto, the bush rings mountedon guide plate protrusions.

FIG. 7 shows a DBC substrate having multiple bush rings and diessimultaneously soldered thereto.

FIG. 8 is a cross-sectional view of a bush ring soldered to a DBCsubstrate.

FIG. 9 is a perspective view of an illustrative set of dies mounted on aDBC substrate.

FIG. 10A is a perspective view of a DBC substrate having multiple diesand bush rings simultaneously soldered thereto.

FIG. 10B is a cross-sectional view of a single bush ring soldered to aDBC substrate.

FIG. 11A shows a frontal view of a press fit power pin.

FIG. 11B is a perspective view of a press fit power pin.

FIG. 12A shows a perspective view of a round power pin.

FIG. 12B shows a top-down view of a round power pin inserted into a bushring.

FIG. 13 is a perspective view of a DBC substrate upon which multipledies and bush rings are simultaneously soldered and of press fit powerpins that are mated with the bush rings.

FIG. 14 is a perspective view of the system shown in FIG. 7 with a mapmolding.

FIG. 15 is a perspective view of the system of FIG. 10A with a mapmolding and a clip.

FIG. 16 is a perspective view of a package containing a DBC substratehaving multiple dies, bush rings and press fit power pins.

FIG. 17 is a flow diagram describing a single reflow technique forassembling power modules.

It should be understood, however, that the specific embodiments given inthe drawings and detailed description thereto do not limit thedisclosure. On the contrary, they provide the foundation for one ofordinary skill to discern the alternative forms, equivalents, andmodifications that are encompassed together with one or more of thegiven embodiments in the scope of the appended claims.

DETAILED DESCRIPTION

Disclosed herein is a power integrated module (PIM) that contains adirect bonded copper (DBC) substrate having a ceramic layer and copperlayers formed on opposing surfaces of the ceramic layer. Semiconductordies and hollow bush rings are mounted and simultaneously soldered tocopper traces on the ceramic layer using a single reflow process. Thebush rings may have shapes that enhance adhesion and electricalconductivity between the rings, the solder joint and the copper traces.The rings are mounted using specialized guide plates, as explainedbelow. Power pins are then inserted into the bush rings, and otherelectronic equipment—such as printed circuit boards—may subsequently becoupled to the power pins. In this manner, reliable electrical pathwaysare formed between this other electronic equipment and the dies with aminimal number of reflows.

FIG. 1 shows a perspective view of a DBC substrate 100. The DBCsubstrate 100 includes a ceramic layer sandwiched between two copperlayers. At least one of the copper layers is in the form of coppertraces—specifically, copper traces 102. Solder units 104 are printed orotherwise deposited onto the copper traces 102 in various locations asdesired. Dies (i.e., semiconductor chips) 106 are mounted onto solderunits (not specifically shown) on the copper traces 102 in variouslocations as desired. The solder units 104 and the solder unitssandwiched between the dies 106 and the copper traces 102 are notreflowed in the system shown in FIG. 1. The specific arrangement ofcopper traces, dies and solder units shown in FIG. 1 is merelyillustrative and does not limit the scope of this disclosure.

FIG. 2 shows a perspective view of a guide plate 200 having multipleprotrusions 202. The guide plate 200 preferably is formed of one or moreplastics, although virtually any material may be suitable. One purposeof the protrusions 202 is to carry hollow bush rings (described belowwith respect to, e.g., FIGS. 3A-3K) so that they may be mounted onto thesolder units 104. Accordingly, the protrusions 202 are formed on theguide plate 200 in a pattern that is a mirror image of the solder units104. In this way, when the guide plate 200 is “flipped over” onto theDBC substrate 100, the protrusions 202 (and the bush rings mountedthereupon) will align with the copper traces and, more specifically,with the solder units 104. Because the protrusions 202 are intended tocarry the hollow bush rings described below, they are formedaccordingly. Thus, the protrusions 202 have dimensions and shapes (e.g.,rectangular cross-section; circular cross-section) that permit the bushrings to be mounted thereupon such that the bush rings do not easilyslide off of the protrusions 202 when the guide plate 200 is flippedover. The protrusions 202 are not so large, however, that theysubstantially deform the bush rings or require substantial force toremove the bush rings from the protrusions 202. In at least someembodiments, each protrusion has a cross-sectional shape that matchesthe cross-sectional shape of a corresponding bush ring. Although theforegoing portion of the disclosure suggests that the protrusions 202are formed as a function of the sizes and shapes of the bush rings, insome embodiments, the sizes and shapes of the protrusions 202 are staticand the sizes and shapes of the bush rings are formed as a function ofthe sizes and shapes of the protrusions 202. All such variations areencompassed within the scope of the disclosure.

FIGS. 3A-3K illustrate perspective views of various bush ringembodiments. The bush rings in each of these figures may be formed usingany suitable conductive material, such as copper. A similar material maybe used in bush ring embodiments falling outside the scope of thesefigures. FIG. 3A shows a hollow bush ring 300 having outer wall surfaces302, inner wall surfaces 304 and an end 306 that lies in a planeperpendicular to the longitudinal axis 308 of the bush ring 300. Thebush ring 300 has a cross-section that is substantially square whenmeasured from outer wall surface to outer wall surface and/or from innerwall surface to inner wall surface. (The term “substantially square,” asused herein, means that the corners of the ring may not be precise rightangles but they may instead be rounded. In addition, a ring may be“substantially square” if its cross-sectional spatial dimensions areidentical or if one such dimension is within 5% of the other suchdimension.) The end 306 is flat, as shown. The scope of disclosure isnot limited to this particular configuration, and all variations andequivalents thereof are contemplated. For instance, the cross-sectionalshape of the bush ring as determined by any measurement may be anysuitable shape (e.g., circular when measured between the inner diametersurfaces or between outer diameter surfaces, as shown in FIG. 3F).

FIG. 3B shows a hollow bush ring 330 having outer wall surfaces 332,inner wall surfaces 334 and an end 336 that lies in a plane or planesperpendicular to the longitudinal axis 338 of the bush ring 330. Thebush ring 330 has a cross-section that is substantially square whenmeasured from outer wall surface to outer wall surface and/or from innerwall surface to inner wall surface. The end 336 has multiple raisedportions and multiple depressed portions. In FIG. 3B, the end 336 hasfour raised portions at the corners of the bush ring and has fourdepressed portions between the raised portions. The raised portions runparallel to the longitudinal axis 338 of the bush ring 330. The scope ofdisclosure is not limited to this particular configuration, and allvariations and equivalents thereof are contemplated.

FIG. 3C shows a hollow bush ring 340 having outer wall surfaces 342,inner wall surfaces 344 and an end 346 that lies in a plane or planesperpendicular to the longitudinal axis 348 of the bush ring 340. Thebush ring 340 has a cross-section that is substantially square whenmeasured from outer wall surface to outer wall surface and/or from innerwall surface to inner wall surface. The end 346 has multiple raisedportions and multiple depressed portions. In FIG. 3C, the end 346 haseight raised portions and eight depressed portions arranged as shown.The raised portions run parallel to the longitudinal axis 348. The scopeof disclosure is not limited to this particular configuration, and allvariations and equivalents thereof are contemplated.

FIG. 3D shows a hollow bush ring 360 having outer wall surfaces 362,inner wall surfaces 364 and an end 366 that lies in a plane or planesperpendicular to the longitudinal axis 368 of the bush ring 360. Thebush ring 360 has a cross-section that is substantially square whenmeasured from outer wall surface to outer wall surface and/or from innerwall surface to inner wall surface. The end 366 has multiple raisedportions and multiple depressed portions. Four depressed portions arepositioned at the corners of the bush ring and four raised portions arepositioned between the depressed portions. The raised portions arecurved so that they extend away from the longitudinal axis 368 of thebush ring. The scope of disclosure is not limited to this particularconfiguration, and all variations and equivalents thereof arecontemplated.

FIG. 3E shows a hollow bush ring 380 having outer wall surfaces 382 andinner wall surfaces 384. The bush ring 380 has an end 386 that lies in aplane or planes perpendicular to the longitudinal axis 388 of the bushring 380. The bush ring 380 has a cross-section that is substantiallysquare when measured from outer wall surface to outer wall surfaceand/or from inner wall surface to inner wall surface. The end 386 hasmultiple raised portions and multiple depressed portions. The raisedportions are curved so that they extend away from the longitudinal axis388 of the bush ring 380. The scope of disclosure is not limited to thisparticular configuration, and all variations and equivalents thereof arecontemplated.

Although non-limiting, in some illustrative embodiments, the bush ringsdepicted in FIGS. 3A-3E have an approximate width of 1.5 mm whenmeasured from outer wall surface to outer wall surface, a length ofapproximately 2.0 mm when measured from end to end, an approximate depthof 0.25 mm when measured from outer wall surface to outer wall surface,and a wall thickness of approximately 0.15-0.25 mm.

FIGS. 3F-3K depict bush rings with generally cylindrical shapes. FIG. 3Fshows a hollow bush ring 301 having an outer wall surface 303 and aninner wall surface 305. The bush ring 301 has an end 307 that lies in aplane perpendicular to the longitudinal axis 309 of the bush ring 301.The bush ring 301 has a cross-section that is substantially circularwhen measured from opposing points on the outer wall surface or innerwall surface. The end 307 is generally flat, as shown. The scope ofdisclosure is not limited to this particular configuration, and allvariations and equivalents thereof are contemplated.

FIG. 3G shows a hollow bush ring 331 having an outer wall surface 333,inner wall surface 335 and an end 337 that lies in a plane or planesperpendicular to the longitudinal axis 339 of the bush ring 331. Thebush ring 331 has a cross-section that is substantially circular whenmeasured between opposing points on the outer wall surface or inner wallsurface. The end 337 has multiple raised portions and multiple depressedportions. In FIG. 3G, the end 337 has four raised portions and fourdepressed portions, as shown. The raised portions run parallel to thelongitudinal axis 339 of the bush ring 331. The scope of disclosure isnot limited to this particular configuration, and all variations andequivalents are contemplated.

FIG. 3H shows a hollow bush ring 341 having an outer wall surface 343,an inner wall surface 345 and an end 347 that lies in a plane or planesperpendicular to the longitudinal axis 349 of the bush ring 341. Thebush ring 341 has a cross-section that is substantially circular whenmeasured between opposing points on the outer wall surface or inner wallsurface. The end 347 has multiple raised portions and multiple depressedportions. In FIG. 3H, the end has eight raised portions and eightdepressed portions, as shown. The raised portions run parallel to thelongitudinal axis 349. The scope of disclosure is not limited to thisparticular configuration, and all variations and equivalents arecontemplated.

FIG. 3I shows a hollow bush ring 361 having an outer wall surface 363,an inner wall surface 365 and an end 367 that lies in a plane or planesperpendicular to the longitudinal axis 369 of the bush ring 361. Thebush ring 361 has a cross-section that is substantially circular whenmeasured from opposing points on the outer wall surface or inner wallsurface. The end 367 has multiple raised portions and multiple depressedportions. The raised portions are curved so that they extend away fromthe longitudinal axis 369 of the bush ring. The scope of disclosure isnot limited to this particular configuration, and all variations andequivalents thereof are contemplated.

FIG. 3J shows a hollow bush ring 381 having an outer wall surface 383and inner wall surface 385. The bush ring 381 has an end 387 that liesin a plane or planes perpendicular to the longitudinal axis 389 of thebush ring 381. The bush ring 381 has a cross-section that issubstantially circular when measured from opposing points on the outerwall surface or the inner wall surface. The end 387 has multiple raisedportions and multiple depressed portions. The raised portions are curvedso that they extend away from the longitudinal axis 389. The raisedportions are more numerous in FIG. 3J than they are in FIG. 31. Thescope of disclosure is not limited to this particular configuration, andall variations and equivalents thereof are contemplated.

FIG. 3K shows a hollow bush ring 391 having an outer wall surface 393and inner wall surface 395. The bush ring 391 has an end 397 that liesin a plane perpendicular to the longitudinal axis 399 of the bush ring391. The bush ring 391 has a cross-section that is substantiallycircular when measured from opposing points on the outer wall surface orinner wall surface. The end 397 comprises a single, continuous, raisedportion 392 that is curved so that it extends away from the longitudinalaxis 399. The scope of disclosure is not limited to this particularconfiguration, and all variations and equivalents thereof arecontemplated.

Although non-limiting, in some illustrative embodiments, the bush ringsdepicted in FIGS. 3F-3K have an approximate diameter of 1.5 mm whenmeasured from outer wall surface to outer wall surface, a length ofapproximately 2.0 mm when measured from end to end, and a wall thicknessof approximately 0.15-0.25 mm.

FIG. 4 shows a perspective view of a guide plate 200 having protrusions202, one of which has a bush ring 300 mounted thereupon. The bush ring300 in this particular example is the same as that shown in FIG. 3A,although other types of bush rings (e.g., those shown in FIGS. 3B-3K)also may be used in lieu of or in combination with the bush ring 300,depending on the shapes of the protrusions 202.

FIG. 5A illustrates a perspective view of the guide plate 200 havingmultiple bush rings 300 mounted on protrusions 202. It also illustratesthe DBC 100 having copper traces 102 upon which solder units 104 anddies 106 are positioned. As arrow 501 indicates, the guide plate 200 isflipped over the DBC 100 so that the protrusions 202—and, morespecifically, the bush rings 300—are aligned with the solder units 104on the copper traces 102. As described below, once the guide plate 200is flipped over onto the DBC 100, a single reflow process is performedso that the solder units 104 and the solder positioned between the dies106 and the copper traces 102 (not specifically shown) aresimultaneously reflowed. As previously explained, the protrusions 202are formed on the guide plate 200 so that when the guide plate 200 isflipped, the protrusions can be aligned with the solder units 104.Alternatively, the solder units 104 are printed in locations that can bealigned with the protrusions 202 of a corresponding guide plate 200. Allsuch variations are included in the scope of this disclosure.

FIG. 5B shows a cross-sectional view of a guide plate vacuum system. Insome cases, the bush rings 300 may have a tendency to slip off of theprotrusions 202 due to gravitational force when the guide plate 200 isflipped. This tendency may be mitigated at least in part by properlysizing the bush rings 300 and/or the protrusions 202. In addition or inthe alternative, a vacuum system may be formed within the guide plate200 and protrusions 202 to suction the bush rings 300 to mitigateslippage during the flipping process. The vacuum system comprises tubing500 in the main body of the guide plate 200, peripheral tubing 502 inthe protrusions 202 and orifices 504 in the surfaces of the protrusions202 through which suction may be applied to the bush rings 300. Thetubing 500 in the main body of the guide plate 200 may terminate at anorifice in any suitable location on the guide plate 200 and may becoupled to a suitable suctioning device external to the guide plate 200.The orifice is formed to mate with tubing that couples to such asuctioning device. The vacuum system of the guide plate 200 is notlimited to the specific configuration shown in FIG. 5B. All variationsand equivalents are contemplated and fall within the scope of thisdisclosure.

FIG. 6 shows a perspective view of a DBC substrate 100 having multiplebush rings 300 and dies 106 simultaneously soldered to copper traces102. The bush rings 300 are mounted on guide plate protrusions (notspecifically shown in FIG. 6). As explained, because the bush rings 300and dies 106 are simultaneously soldered to the copper traces 102, onlya single reflow process is required. The guide plate 200 and protrusionsare subsequently removed. The solder connection between the bush rings300 and the copper traces 102 is sufficiently strong so that the forceapplied to remove the protrusions from the bush rings 300 does not causethe bush rings 300 to become disconnected from the copper traces 102.

FIG. 7 shows the DBC substrate 100 having multiple bush rings 300 anddies 106 simultaneously soldered to copper traces 102. After the bushrings 300 are soldered to the copper traces 102 (as indicated by solderunits/joints 104), the guide plate 200 and protrusions 202 are removed,leaving the structure shown in FIG. 7. At this stage, the dies 106 maybe electrically coupled to various copper traces (and, thus, to the bushrings mounted on those traces) using any suitable electrical connections(e.g., wire bonds) as desired.

FIG. 8 is a cross-sectional view of a bush ring 300 soldered to a coppertrace 102 of the DBC substrate 100. The solder unit/joint 104electrically and mechanically couples the bush ring 300 to the coppertrace 102.

FIG. 9 is a perspective view of another illustrative set of dies 904mounted on copper traces 902 which, in turn, are formed on the ceramiclayer of a DBC substrate 900. As with the system shown in FIG. 5A, aguide plate having protrusion-mounted bush rings is flipped over ontothe copper traces 902 and is subsequently removed after a single reflowprocess, leaving the structure shown in FIG. 10A. Specifically, FIG. 10Ashows the DBC substrate 900 on which copper traces 902 are formed. Dies904 and bush rings 906 were simultaneously soldered to the copper traces902. FIG. 10B is a cross-sectional view of a single bush ring 906soldered to a copper trace 902 of the DBC substrate 900. The solderjoint 908 mechanically and electrically couples the bush ring 906 to thecopper trace 902. As explained, the solder joint 908 is formedsimultaneously with joints between dies and the copper trace(s) during asingle reflow process.

FIG. 11A shows a frontal view of a press fit power pin 1100 that may beinserted into any of the bush rings described herein. The pin 1100 has ahead 1102 with a tapering shape—i.e., it has a width that is greatest inthe center 1106 of the head 1102 and is lesser in the proximal area 1104and distal area 1108 of the head 1102. The head 1102 also comprises anorifice 1112 that extends along the longitudinal axis 1114 of the pin1100. The head 1102 further includes a distal tip 1116 that may beincluded in one head, both heads (e.g., the tip is omitted from opposinghead 1110) or neither head. The pin 1100 is appropriately sized relativeto the bush ring in which it will be inserted so that the pin 1100 andbush ring maintain electrical contact and so that the pin 1100 isadequately mechanically coupled to the bush ring. In at least someembodiments, the head of the pin 1100 that is to be inserted into thebush ring has a larger dimension than at least one dimension of the bushring such that the bush ring deforms (e.g., by 1 mm-2 mm) upon insertionof the pin. FIG. 11B shows a perspective view of the power pin 1100.

FIG. 12A shows a perspective view of a round-head power pin 1200. Theheads 1202, 1204 may be shaped as shown—i.e., to conically taper andterminate with a flat end that is in a plane perpendicular to thelongitudinal axis 1206 of the pin 1200. In alternative embodiments,round ends are used in lieu of flat ends. Any and all variations andequivalents of such heads are contemplated and fall within the scope ofthis disclosure. As with the pin 1100, the pin 1200 is appropriatelysized relative to the bush ring in which it will be inserted so that thepin 1200 and bush ring maintain electrical contact and so that the pin1200 is adequately mechanically coupled to the bush ring. In at leastsome embodiments, the head of the pin 1200 that is to be inserted intothe bush ring has a larger dimension than at least one dimension of thebush ring such that the bush ring deforms (e.g., by 1 mm-2mm) uponinsertion of the pin. FIG. 12B shows a top-down view of a power pin 1200inserted into a bush ring 1250 with adequate mechanical and electricalcontact. As shown, the bush ring 1250 has a substantially squarecross-sectional shape and is electrically and mechanically coupled to acopper trace 1252 via a solder unit 1254. As also shown, the diameter ofthe pin 1200 slightly exceeds the dimensions of the bush ring 1250 sothat the bush ring 1250 is slightly deformed. This ensures adequatemechanical coupling between pins and bush rings.

FIG. 13 is a perspective view of a DBC substrate 900 having coppertraces 902 upon which multiple dies 904 and bush rings 906 aresimultaneously soldered and of press fit power pins 1100 that are matedwith the bush rings 906. The pins 1100 may be coupled with otherelectronic equipment—for instance, a printed circuit board that islowered onto the pins 1100 and that contains orifices through which thepins 1100 may pass. Such orifices may contain electrical pathways aroundtheir periphery so that they can establish electrical contact with thepower pins 1100. The scope of disclosure, however, is not limited tocoupling any particular type of electronic equipment to the power pins1100.

FIG. 14 is a perspective view of the system shown in FIG. 7 with a mapmolding 1400 that is formed using well-known techniques (e.g., usingsuitable flat mold chases). The mold 1400 is formed after all necessaryor desired structural features are complete—for instance, any necessarywire bond couplings between dies and copper traces are established priorto forming the mold. The mold 1400 is made of any suitable material(e.g., an epoxy resin, SUMITOMO® G760, HITACHI® CEL9220) and hasdimensions that are a function of the system of FIG. 7. Morespecifically, the length and width of the mold 1400 match the length andwidth of the DBC substrate 100. The top surface 1402 of the mold 1400 isflat and the thickness of the mold 1400 is such that the top surface1402 is flush with the top ends of the bush rings 300, as shown. Othertypes of molds and other mold formation techniques are known,contemplated and fall within the scope of the disclosure.

A similar map molding may be applied to the system of FIG. 10A, as shownin FIG. 15. Specifically, FIG. 15 shows a map molding 1500 applied tothe system of FIG. 10A so that it covers the entirety of the system anddoes not leave substrate 900 exposed. Power pins—for instance, round toppower pins 1200—may be inserted into the bush rings 906. As is alsoshown, a metal or plastic clip 1502 may be mounted on the mold 1400 andmay subsequently be used to mechanically fasten the structure to anothercomponent, such as a heat sink. A metal or plastic clip may also be usedwith the map molding system of FIG. 14. Furthermore, although FIG. 15depicts the use of round top power pins 1200, other types of pins, suchas press fit power pins, may be used instead.

FIG. 16 is a perspective view of a package 1600 containing a DBCsubstrate having multiple dies, bush rings and press fit power pins1100. The pins 1100 protrude through the orifices 1602 of the package1600. The package 1600 preferably is composed of a non-conductingmaterial (e.g., one or more plastics). The package 1600 may be mounteddirectly over the substrate, dies and bush ring assembly or the assemblymay first be map molded as shown in FIG. 15 prior to mounting thepackage 1600. The structural features of the package 1600 areapplication-specific and may be formed as desired.

FIG. 17 is a flow diagram describing a single reflow technique 1700 forassembling power modules. The method 1700 includes providing a directbonded copper (DBC) substrate that includes a plurality of copper traces(step 1702). As explained, such a DBC substrate typically includes aceramic layer sandwiched between two copper layers, at least one ofwhich includes multiple copper traces suitable for carrying electricalsignals. The method 1700 next includes providing a guide plate havingprotrusions on a surface of the guide plate (step 1704). Theprotrusions' sizes and shapes are application-specific and aredetermined based on the sizes and shapes of the corresponding bush ringsthat are to be mounted on the protrusions. Alternatively, the bushrings' sizes and shapes are determined based on the protrusions' sizesand shapes. The method 1700 further includes mounting the hollow bushrings onto the protrusions (step 1706). In at least some embodiments,the bush rings maintain their position on the protrusions using a vacuumsystem built into the guide plate and protrusions. If used, such avacuum system is activated when the bush rings are mounted onto theprotrusions and is not deactivated until the bush rings have beensecurely soldered to the copper traces. The method 1700 subsequentlycomprises mounting the bush rings onto the copper traces by aligning theprotrusions (or bush rings) of the guide plates with the coppertraces—and, more specifically, with solder units deposited on the coppertraces (step 1708). The method 1700 includes attaching the bush ringsand one or more dies to the copper traces by simultaneously reflowingthe solder units between the bush rings and copper traces and betweenthe dies and copper traces (step 1710). Finally, after the simultaneousreflow, the guide plate and protrusions are removed from the bush rings(step 1712). The method 1700 may be modified as desired, such as byadding, deleting or modifying steps. For instance, power pins may beinserted into the bush rings, wire bonds may be established between diesand copper traces, map molding may be formed on the DBC substrate/bushring/die structure, a package may be formed around the structure, and/ora printed circuit board may be coupled to the power pins.

Numerous other variations and modifications will become apparent tothose skilled in the art once the above disclosure is fully appreciated.It is intended that the following claims be interpreted to embrace allsuch variations, modifications and equivalents. In addition, the term“or” should be interpreted in an inclusive sense.

What is claimed is:
 1. A method, comprising: providing a direct bondedcopper (DBC) substrate including a plurality of copper traces; providinga guide plate having protrusions on a surface of the guide plate;mounting hollow bush rings onto the protrusions; mounting the bush ringsonto the copper traces by aligning the protrusions of the guide platewith solder units on said copper traces; attaching the bush rings andone or more dies to the copper traces by simultaneously reflowing saidsolder units and other solder units positioned between the dies and thecopper traces; and after said simultaneous reflow, removing theprotrusions from the bush rings.
 2. The method of claim 1, furthercomprising using a vacuum system to retain the bush rings on theprotrusions.
 3. The method of claim 2, further comprising disabling thevacuum system prior to removing the protrusions from the bush rings. 4.The method of claim 1, further comprising inserting power pins into thebush rings.
 5. The method of claim 4, wherein at least one of the powerpins has a dimension that exceeds an internal wall surface-to-internalwall surface dimension of a corresponding bush ring.
 6. The method ofclaim 4, wherein each head of one or more of the power pins has a widththat is greatest in the center of the head and comprises an orifice. 7.The method of claim 4, further comprising establishing electricalcontact between said power pins and a printed circuit board (PCB). 8.The method of claim 1, wherein at least one of the bush rings has ashape that is selected from the group consisting of: a cross-sectionthat is substantially square when measured from outer wall surface toouter wall surface and one end that is flat, said end located in a planethat is perpendicular to the longitudinal axis of the bush ring; across-section that is substantially square when measured from outer wallsurface to outer wall surface and one end at which the wall has multipleraised portions and multiple depressed portions, said end located in aplane that is perpendicular to the longitudinal axis of the bush ring;and a cross-section that is substantially square when measured fromouter wall surface to outer wall surface and one end at which the wallhas multiple raised portions and multiple depressed portions, saidraised portions extending away from the longitudinal axis of the bushring, said end located in a plane that is perpendicular to thelongitudinal axis of the bush ring.
 9. The method of claim 1, furthercomprising depositing a molding onto the DBC, bush rings and dies, asurface of the molding being flush with the end of at least one of saidbush rings, said end located in a plane that is perpendicular to thelongitudinal axis of the bush ring.
 10. The method of claim 9, furthercomprising using a metal or plastic clip to fasten the molding to a heatsink.
 11. A system, comprising: a direct bonded copper (DBC) substrateincluding a ceramic layer and copper traces on a surface of the ceramiclayer; hollow bush rings soldered to the copper traces; and a guideplate having protrusions mated with the bush rings, wherein each of saidbush rings has an end at which the wall of the bush ring has multipleraised portions and multiple depressed portions, said end located in aplane that is perpendicular to the longitudinal axis of the bush ring.12. The system of claim 11, wherein said ends are soldered to the coppertraces.
 13. The system of claim 11, wherein said raised portions extendaway from the longitudinal axis of the bush ring.
 14. The system ofclaim 11, wherein said raised portions are parallel to the longitudinalaxis of the bush ring.
 15. The system of claim 11, wherein said bushrings have substantially square cross sections when measured from outerwall surface to outer wall surface.
 16. The system of claim 11, furthercomprising a die soldered to one of the copper traces.
 17. The system ofclaim 11, further comprising a vacuum system having air passagespositioned in the guide plate and in at least one of the protrusions.18. A system, comprising: a package; a plurality of pins protrudingthrough orifices in the package; a direct bonded copper (DBC) substratehaving a ceramic layer and multiple copper traces on the ceramic layer,said copper traces soldered to hollow bush rings within which said pinsare positioned; and one or more dies soldered to one or more of thecopper traces and electrically coupled to one or more of the pins,wherein each of the bush rings has an end at which the bush ring wallhas raised portions and depressed portions, said end in a plane that isperpendicular to the longitudinal axis of the bush ring, wherein saidends are soldered to the copper traces.
 19. The system of claim 18,wherein each of said pins has two heads, at least one of said two headshaving a tapering shape and an orifice.
 20. The system of claim 18,wherein said raised portions of the bush ring wall extend away from thelongitudinal axis of the bush ring.